In diagnostics, aqueous fluids, including biological fluids such as whole blood, plasma, nasal secretion, sputum, saliva, urine, sweat, and cerebrospinal fluids, are routinely analyzed for specific components that are clinically important for monitoring and diagnosis.
In-vitro diagnostic devices are used in various settings including hospitals, clinics, alternative care sites, and in the home. These devices have been developed by various manufacturers to enable clinical professionals and non-professionals to make accurate decisions for the diagnosis and management of certain conditions. Such point-of-care devices are often used to analyze blood chemistry such as electrolytes and pH. For example, diabetics routinely use diagnostic test strips to monitor blood glucose concentrations and bacterial contamination in food and water is tested by regulatory environmental and other agencies, while chemical contamination of water sources is of interest to environmental and water supply companies.
Manufacturers of in-vitro diagnostic devices strive toward three important goals: to reduce the amount of fluid required for the test, to reduce the time needed for the test, and to improve the accuracy of the device. The hydrophilic components of the test device play a crucial role in achieving these goals. These test devices typically contain microfluidic capillary channels that allow for the transport of biological fluid from a sample inlet port to a detection zone of the device. Typically, the specimen is deposited at an inlet port of the test strip and the sample fluid is drawn into the device mechanically or by capillary flow. For capillary action to occur, the walls of the channel should reliably demonstrate hydrophilic characteristics and capillaries forming the microfluidic channels should spontaneously fill in a rapid and consistent manner when in contact with the sample fluid. The fluid should flow consistently, wetting the entire analysis zone without stalling during transit through the channels.
A hydrophilic film is typically used as a top cover, with spacers constructed of a non-hydrophilic pressure sensitive adhesive or heat seal. Additionally, many tests are designed on rigid PMMA, glass or COC cards which channels machine cut that would require a hydrophilic top seal to enclose the channels and provide the hydrophilic flow capabilities.
WO 2002/085185 describes the use of certain hydrophilic adhesives in combination with or which can replace hydrophilic films in some diagnostic device constructions. These hydrophilic adhesives serve to provide the combined advantage of reducing the surface tension of the analyte to promote wicking while also adhering components of the device together.
The adhesives and devices of the '185 publication are useful, but the art would benefit from continuing improvements. In particular, certain constructions of diagnostic devices have been disfavored because known hydrophilic technologies relied on an incompatibility of surface active agent and polymer matrix of the adhesive to achieve hydrophilicity. While this provided the desired result, it results in blooming of the surface active agent to the surface of the adhesive, which ultimately reduces the consistency of the hydrophilic properties when used in certain constructions.
These and other drawbacks are present in the current art.